MySQL Maintenance Window and Failover

[Pavel Madr]

Hi,

Please, does somebody know how cloud MySQL behaves during maintenance window if also failover is enabled?

Are master and failover machine maintaining at the same time?

Or is master upgraded at first, so the failover machine can serve data meanwhile?

Short DB connection interruptions are ok for our solution, but a few minutes without DB is quite a problem.

[Navi Aujla (Google Cloud Support)]

Hello Pavel 

You can define the maintenance window and maintenance timing for your Mysql second generation instances [1]. Please note, there are impacts of changing instance setting as described in public documentation help link [2]. 

I was able to find documentation [3] stating "Note, however, that not all instances are upgraded to the new release at the same time." But it do not confirm which server upgrades first that is master or the replica server and if both get upgrade at same time during maintenance window. I will get back to you with the information. 

[1] https://cloud.google.com/sql/docs/mysql/instance-settings#settings-2ndge
[2] https://cloud.google.com/sql/docs/mysql/instance-settings#impact

[3] https://cloud.google.com/sql/faq#maintenancerestart

[Navi Aujla (Google Cloud Support)]

Hello Pavel, 

I verified with backend team. Maintenance window may overlap for master and fail-over server, and in such case, the upgrade will happen for both at the same time.  While being updated the fail-over and master may not serve. Hence, recommend placing exponential backoff in place as standard error handling strategy. For more information on managing connections and exponential backoff, please refer to public documentation link [1][2].

[1] https://cloud.google.com/sql/faq#connections
[2] https://cloud.google.com/storage/docs/exponential-backoff

[Pavel Madr]

Hello Navi,

Thank you. I'll use exponential backoff.

Best Regards,

Pavel Madr